The presentation of information received from a remote information source in an accordingly arranged device is a well-known technical concept, e.g. in television and radio. An information presentation device of this kind will typically contain an information transmission receiver for receiving information transmissions, an information extractor for extracting presentation information that is to be presented, from such a received information transmission, and finally an information presenter for presenting the extracted presentation information.
Depending on the specific method of transmission between the remote source and the presentation device, the transmission receiver will be appropriately arranged. For example, if the information transmission is sent via a radio link, then the information transmission receiver shall have an antenna and appropriate receiving hardware. Alternatively, if the information transmissions are sent over a wire-bound network, then the information transmission receiver shall be appropriately arranged to receive such signals, i.e. will be connected to the wire-bound network in suitable fashion.
Equally, the extracting of presentation information, which can e.g. be an audio signal, a video signal or any mixed form of multimedia signal, will be conducted in accordance with the specific transmissions scheme employed. For example, if the transmission signal is an analogue signal, then the information extractor will be arranged to process the analogue signal (e.g. a frequency modulated radio) in order to extract the presentation information (e.g. an audio signal). As another example, an information extractor can also be a digital player, such as a video reproduction device that is arranged to receive a digital stream (e.g. coded in MPEG 3 or 4) and arranged to output a suitable signal (e.g. an RGB signal) for an information presenter, such as a TV or computer screen.
Finally, similar to the information transmission receiver and the information extractor, the information presenter will also depend on the type of information being presented, e.g. can be an audio interface (such as a loudspeaker and underlying hardware) if an audio signal is to be presented, a video interface (such as a screen and its underlying hardware) if a video signal is to be presented, etc.
A multitude of different concepts is employed in connection with the above-described basic idea of conveying presentation information from a remote source to an appropriate presentation device. For example, there exists the concept of broadcasting, which means that a source simply sends out information transmissions to a certain area (where said area can be defined physically as a transmission range, or logically as a certain set of addresses reachable in a network using an addressing scheme), where it is up to prospective receivers to “tune-in” to such transmissions, or the concept of multicasting, where a source sends out transmissions to a restricted plurality of destinations, or the concept of unicasting, where a source sends out a transmission to one destination. Naturally, the implementation of such concepts depends on the transmission technology used between the source and the receiving presentation device.
In order to ensure that the transmission from a source to a receiver is conducted appropriately, a number of mechanisms are known, such as forward error correction (FEC), which means that the source tries to appropriately prepare the signal being sent to the receiver such that it may be correctly received, e.g. by appropriately adjusting that transmission power or by introducing redundancy, and backward error correction, which implies communication from the receiver to the sender regarding errors, the most prominent example of which is automatic retransmission request (ARQ), which means that the receiver makes a determination whether a signal has correctly been received, and if not, automatically requests the sender (or source) to retransmit.
Beyond the well known concept of ARQ, which is implemented at the transmission receipt level, and ensures that the signal directly received at the input is indeed identical to what the sender (source) transmitted, it is also known to perform a type of service quality monitoring in a system consisting of a source and a receiver, where subsequent processing of the received input signal is also taken into account. Namely, ITU-T recommendation H.323 (11/96) proposes a maintenance loop-back mechanism according to which a received media stream, after it has been decoded by a codec, is looped back into the sending terminal of the codec, in order to be sent back to the source entity, such that the source entity can perform quality control.
In recent years, the advent of digital packet-based communication networks, such as the Internet, has led to extensive efforts for implementing systems of conveying presentation information from a remote source to an information presentation device over such a network. For example, Internet radio and Internet TV are already in use. Especially in connection with Internet TV, there are ongoing activities for implementing more sophisticated concepts and features than simple broadcasting. For example, protection against copying or eavesdropping is an issue, as e.g. discussed in connection with the High Bandwidth Digital Content Protection system, information on which is available at www.digital-ct.com, ISBN 0 9675129-4-8. Another issue is that of performing accounting for content sent over the Internet. The article “Internet accounting”, by Aiko Pras et al., in IEEE Communication Magazine, May 2001, pages 108-113 summarizes such efforts. In this article is e.g. discussed to provide a system referred to as “billing after acknowledgements”, which means that a stream of information that is to be sent from a source to a paying receiver is divided into a plurality of “units”, where a unit may be defined in terms of data amount or as a unit of time, and after the sending of a given unit, the subsequent units are only sent if an appropriate acknowledgement for billing is received from the receiver to the billed.
There is, therefore, a need for an improved system of conveying presentation information from a remote source to an information presentation device of the above-described kind.